The current AWS EC2 AMI for UCS 4.1 shows the following hint:
ssh -i <path/to/privatekey> root@<IP address> passwd
This will print the password and its confirmation in plain text.
When -t is added the password is not shown.
From man ssh 5:
-t Force pseudo-terminal allocation. This can be used to execute arbitrary screen-based programs on a remote machine, which can be very useful, e.g. when implementing menu services. Multiple -t options force tty allocation, even if ssh has no local tty.